Conventional dispensers for liquids having relatively high viscosities, such as heavy duty soaps, shampoos, tomato ketchup, mayonnaise, tooth paste, high viscosity oils or the like, oftentimes take the form of a semi-rigid plastic container having an openable closure cap or a reciprocal dispensing valve mounted thereon. Conventional dispensers of this type are relatively expensive to manufacture, are prone to malfunction and leakage and normally do not insure that a pre-measured charge of the liquid will be efficiently dispensed therefrom.
Other types of conventional dispensers include thin-walled plastic pouches that are heat sealed to retain a liquid product therein. A corner of the pouch is either ripped open to dispense the product or a closure plug is used for this purpose. Further, U.S. Pat. Nos. 3,009,498; 3,184,121; 3,815,794; and 4,252,257 and Canadian Patent No. 735,289 disclose pouches or bags which provide various types of closures to seal the bags after product has been dispensed therefrom. Bags of this type are incapable of efficiently dispensing relatively high viscosity liquids (e.g., 3,000 to 14,000 centipoises) and require mechanical manipulation or other extraneous forces to open and close the valves thereof.
The dispenser pouches disclosed in applicant's U.S. Pat. Nos. 5,000,350 and 5,067,635 have solved the above prior art problems by providing systems that function efficiently to dispense liquids having a wide variety of viscosities. However, when liquids having relatively high viscosities (e.g., in excess of 3,000 centipoises) were used in the so called deep-drawn pouch of the type shown in FIGS. 4 and 5 of U.S. Pat. No. 5,000,350, the dispensing efficiency of the pouch was found to lessen when the contents of the pouch approached empty.